TECHCRUNCH: Square is in the process of building up a series of products and services that use its payments platform as a foundation. The latest, launching today, is an email marketing tool gives physical businesses the same advantages of online stores.

Square Marketing is a set of tools that lets brick and mortar businesses act more like online retailers when it comes to setting up — and tracking the effectiveness of — marketing campaigns. Email marketing has grown more sophisticated over the years, and the space is crowded with companies like MailChimp, Marketo, Salesforce and Constant Contact. Now Square is throwing itself in the mix, hoping to differentiate itself the same way that it’s making that effort with Square capital: data.

The tool allows users of Square’s payments services to click through an ‘engage your customers’ link from their Insights dashboard, which gives them an overview of their current business — collated from data gathered via sales. The dashboard has been around a while, but it has existed without a way to actually do anything about the trends it was telling businesses that they were experiencing.

What if, for instance, a business saw that they had a boom of new customers, but at the same time were seeing a sloping graph of return visits by old customers? They might bounce out to an email tool to craft a campaign and send it to a list of emails gathered via paper, or by hand using clerks at the counter. A retail store I worked at used to gather them by requiring an email with every transaction — but that requirement can slow down transactions, and is really only practical if a user terminal was involved in the flow. And half the time you end up with fake emails and unverifiable information.

Square’s data is already easier to gather and far more likely to be accurate because it’s tied directly to the customer’s payment accounts. If they’re paying by card, the Square flow asks them for an email for a receipt — and because you’re talking about money here people are more likely to give accurate info.

All of that leads to a Square business having a core list of emails for customers that is ready to act on. Enter Square Marketing.

Firing up the tool provides you with a list of customers pre-sorted into three groups: loyal customers, casual customers and lapsed customers. Already you’re far ahead of a dumb list of emails, which contain no such contextual data. You can also add your own lists of emails gathered via conventional means.

You can choose groups based on trends that you’re seeing and the type of campaign you want to create. If you have a loyal customer, you’re going to want to send them notices of special events or community notices. If they’re a casual customer you could offer them a time-based discount. A lapsed customer could be lured back by offering them a promo to encourage them to walk back in the door — like the one below from Baking Betty’s.

The tool will, as many others already do, show you delivery data as well as ‘read’ notifications for your emails. But Square takes the next step here by allowing you to actually see if those customers take action on your email with a visit and a purchase.

It’s hard to overstate the importance of being able to directly track the return on your investment in this email marketing by equating it with dollars spent in your establishment.

Unless you’ve been in small business retail or sales and have tried to craft a marketing campaign and measure its effectiveness, the impact of this is going to be hard to get across. The process is somewhere between using a dowsing rod and the dark arts.

This is the holy grail of marketing, and has been possible online via tracking cookies, promo codes and other means. But it’s been notoriously difficult to do in store because people are flaky and either won’t tell you the source of their visit or the source of their promotional passphrase that you’ve tried to attach to a campaign.

Square has effectively attached a tracking cookie to a physical person because it knows what they use to pay you.

This is the kind of thing that has made marketers so hot and bothered about thepossibilities of beacons — small devices that track visitors via apps installed on their smartphones. But square does it without any additional hardware by leveraging the fact that they own the payments stack.

The emails are affordable, if a bit pricier than similar levels in services like Mailchimp. You can pay $0.10 per email on an ‘as you go’ basis or $15/mo for unlimited emails to 500 customers. The cost isn’t quite analogous to any other service because of Square’s unique ability to track customer visits and spend, but those are differentiators that will depend on messaging and price is always a strong pull — especially for small businesses.

Square Marketing feels like a solid add on for current customers. It lets them cut down on the number of moving parts they have to keep track of to make their email marketing effective. Instead of hand collected lists, a CRM, an email service and tracking software to attempt to link those emails to return customers hey can just click a link in the insights dashboard of their Square account.

Square says that sellers using the service have seen open and redemption rates that are double the ‘industry average’ and that Square sellers generated almost $1M in sales tied to promo redemptions.

But that’s for existing customers. There is a wide open question of whether these kinds of perks – ready cash, slick analytics tools and cleverly executed email marketing — will lead to new business, not just retention and satisfaction. Both of those are worthy goals, of course, but growth is key.

Also, I’d love to see the flow of Square Marketing applied to a native mobile app for Square sellers. The setup and execution of a campaign are so simple already that it makes sense to let those sellers using mobile devices primarily to collect campaigns to do it just as easy as those sitting at their desktops. When a food truck can effectively craft marketing campaigns and track business even when their business is inherently itinerant — and they can do it right from their phones — that’s a tectonic shift in that arena.

The suite of tools Square is building out — like Register and Capital — make a very strong case for adopting its payments platform, which is the end goal. But growth is core to Square’s underlying payments business, which thrives on scale. So whether that resonates with new users will be key.